Tilting back chair



g- 1 P. MOND'Y 2,563,951

TILTING BACK CHAIR Filed April 5, 1947 5 Sheets-Sheet 1 Fig.1

IN V EN TOR.

Aug. 14, 1951 P. MONDY 2,563,951

i TILTING BACK CHAIR Filed April 5, 1947 5 Sheets-Sheet 2 m INVENTOR. 35 B 7 0K61 Maud Aug. 14, 1951 P. MONDY 2,563,951

TILTING BACK CHAIR Filed April 5, 1947 5 Sheets-Sheet 5 IN V EN TOR.

E eiel' IToratlg Aug. 14, 1951 P. MONDY 2,563,951

TILTING BACK CHAIQR Filed @pril 5, 1947 5 Sheets-Sheet 4 IN V ENTOR.

Jr Peter 7700f! Patented Aug. 14, 195i [TED STATES NT OFFEQ 11 Claims. 1 My invention relates generally to chairs and has to do particularly with a chair wherein one or more of the chair portions which engage and support the body of the user are adjustable to provide maximum comfort for the user.

An object of my invention is to provide an improved chair of the foregoing character.

Another object is to provide an adjustable chair which may be formed form a. relatively small number of simple and inexpensive parts with a minimum of machined or close-fitting surfaces,

and which may be assembled readily with a minimum of fitting or adjustment.

Still another object of the invention is to provide an improved height adjusting mechanism for a chair of the type having a rotatable seat, which mechanism after a simple adjustment, may be actuated by simply rotating the chair seat to the desired height.

Another object is to provide a height adjusting mechanism for a chair which is simple and rugged in construction, and easy to operate and which is substantially concealed within the chair base and seat supporting post and thus is protected against the entry of dirt and dust, presents a neat and attractive appearance and eliminates the likeli- .hood of damage to the clothes of the user.

Another object is to provide an improved mechanism for adjusting the angle of the chair back relatively to its supporting means, which is simple and sturdy, readily adjustable by the user from a sitting position in the chair, which does not require that the members be accurately dimensioned or carefully fitted, and which securely holds the chair back in any position to which adjusted.

A further object is to provide a chair back angle adjusting mechanism wherein the relative- .ly adjustable members may be firmly secured in user from a sitting position in the chair and which permits rocking movement of the back cushion on its support for increased comfort of the user as he shifts his position in the chair.

Further and specific objects of the invention are to provide an improved swivel bearing which is simple in construction and which firmly mounts the chair seat supporting post for rotation in the base in a stable upright position; to provide a seat suporting post which is substantially unencumbered by external adjusting mechanism; to provide a height adjusting mechanism which may be operated to adjust the chair seat to the desired height without soiling the hands or clothes; to provide an improved chair back tilting mechanism which may be operated by the user while sitting in the chair to adjust the resistance to tilting of the chair back; to provide a back mounting mechanism which is self-aligning whereby any stresses applied thereto during use are equalized and distortion or bending of the back adjusting mechanism is prevented; and to provide a back angle adjusting mechanism having a manually operable clamping mechanism which when tightened to a predetermined extent is effective to exert a substantially uniform holding eifect on the angularly adjusted members throughout the entire range of adjustment thereof.

Other objects and advantages of the invention will appear from the following description taken in connection with the appended drawings, wherein:

Figure 1 is a perspective view showing a chair constructed in accordance with my invention;

Fig. 2 is an enlarged fragmentary Side elevatio'nal view of a portion of the chair shown in Fig. l with certain of the parts broken away and sectioned for a clearer understanding of the construction;

Fig. 3 is a fragmentary side elevational view of the latching device for the height-adjusting mechanism shown in Fig. 2;

Fig. 4 is an enlarged fragmentary, perspective and partially exploded view of a portion of the chair shown in Fig. 1 with certain of the parts broken away and in section for a clearer understanding of the construction;

Fig. 5 is an enlarged fragmentary, sectional View taken approximately along the line 55 of Fig. 2;

Fig. 6 is a fragmentary view showing a, portion of the structure of Fig; 2 with certain of the parts broken away and in section for a clearer understanding of the construction; and

Fig. 7 is a perspective view showing the back rest support of the chair shown in Fig. l and with the back rest indicated in broken lines.-

A chair embodying the present invention is illustrated in Fig. 1 and comprises generally a base Ill, a supporting post H rotatably mounted inthe base Ill and adapted for vertical adjustment therein, a seat |2 mounted on the seat-supporting post and a back rest support |3 extending upwardly at the rear of the seat l2 and carrying a back rest M.

The base In may be formed in any suitable manner but preferably is formed by casting it from light metal such as aluminum. The base may have the usual four legs which preferably are of hollow form but which are not shown or described in detail as they may be of any suitable construction. For supporting the chair post II in the base 16 a generally cylindrical socket I9 is provided (Fig. 2) preferably by casting a hub 20 integrally with the base. The hub 26 is substantially housed and concealed within the hollow base l6 and is formed with open upper and lower ends.

A generally cylindrical spindle 2 I, which may be formed from a steel tube, is journaled in the hub 20 by combined thrust and side-bearing means which maintain the vertical position of the spindle 2| but permits free rotation thereof in the hub 23. The bearing means includes an upper thrust bearing 22 which preferably takes the form of an annular self-lubricating ring pressed into the upper end of the hub 20 and seated against a shoulder 23 therein. The spindle 2| is supported by a flange 24 which may be formed integrally with the tube from which the spindle 2| is formed but preferably is formed as a separate ring and welded to the spindle tube. The spindle 2| is retained in the hub 20 by a retaining ring 25 preferably formed in two sections (Fig. 4) and secured to the base l6 (Fig. 2) as by screws 25 which are threaded into an upstanding portion 21 of the hub 26 which surrounds the upper open end of the socket l9. The flange 24 is formed with a peripheral groove 28 adapted to receive the retaining ring 25 and provide therewith means for preventing dust or other small foreign objects from entering the bearing 22. The bearing means also includes a lower bearing 3| which takes the form of an annular self-lubricating ring mounted in the lower end of the hub 20 by an adapter or mounting ring 29 pressed into the lower end of the hub and seated against a shoulder 30. The lower bearing 3| aids in maintaining the spindle in vertical position.

The spindle 2| supports a threaded heightadjusting element 34 which preferably is formed as a threaded stud secured rigidly in an end wall or fioor 35 secured to or integral with the tubular spindle body.

The supporting stem or post H is received in the spindle 2| in telescoping relation therewith, the fit between these members being sufficiently snug so that the post H is supported firmly in a vertical position by the spindle 2| but is sufficiently free therein to permit both axial sliding and angular rotational movement of the post II in the spindle 2|. The supporting stem or post carries at its lower end a threaded adjusting member 36 adapted to be screwed on to-the threaded stud 34 for adjustably mounting the supporting post II on the stud 34. The post preferably is formed as a tubular member and receives therein the adjusting member 36 which preferably takes the form of a nut having laterally extending diametrically opposed ears 3! adapted to enter opposed slots 38 (Fig. 4) formed in the ,side walls of the supporting post adjacent its lower end. The slots 38 are of sufficient length to receive the ears 3! when the nut 36 is tilted and inserted through the open lower end of the hollow post The portion 39 of the post in which the slots 38 are formed may be reduced in diameter to permit the ears 31 to be engaged by the lower edges of the slots inwardly of the ends of the ears sufiiciently to insure that the ears will not slip out of the slots and at the same time permit the ears to be made of such lateral extent that they clear the inner wall of the spindle. The body of the nut 33 may be of lesser axial length than the ears 3? in order to permit the nut 36 to be inserted in the open end of the post H and locked into position to bring the cars into their slots 38 readily and without necessitating lengthening the slots substantially beyond the length of the ears to permit this manipulation of the nut.

After assembly of the nut 36 in its position (Fig. 2) in the end of the post H and with the ears 3'! in their slots 38 the post II and spindle 2| are assembled by inserting the lower end of the post II in the upper open end of the spindle 2|. The nut 36 is then screwed on to the stud 34 by rotating the post II, the upper end of the stud being non-threaded and reduced in diameter to permit easy insertion of the stud end in the nut. It will be seen from the foregoing that since the spindle 2| is rotatably supported in the base It) the spindle, together with the post may be rotated together as a unit relative to the base, in which case the post II will remain in the same position of vertical adjustment with respect to the spindle and to the base I6. On the other hand, if the spindle is held against rotation in the base and the post H is rotated, the nut 36 will advance along the adjusting stud to displace the post axially with respect to the spindle 2| to raise or lower the post according to the direction in which it is rotated.

Means are provided for selectively locking the spindle either to the post II for rotation therewith so that when the latter is rotated no height adjustment takes place or for locking the spindle 2| to the base I!) whereby, upon rotation of the post, vertical adjustment of the post is effected relative to the base. This means includes a two-position toggle latch mechanism secured to a portion of the spindle 2| which projects upwardly out of the socket l9 and preferably located in a position where it can be operated by the user while seated in the chair. The latch mechanism includes a latch element 39 pivotally mounted as by shoulder screws 53 secured in spaced brackets 5| attached to the spindle 2| as by welding. The latch element 49 preferably is formed of sheet material bent into the form of a yoke the sides of which have projecting portions 52 providing locking toes adapted to enter an elongated opening 53 in the post I when the latch element is in its upper position, the opening 53 being of such vertical length that it will receive the latch element 49 through the entire range of vertical adjustment of the post Each of the sides of the latch member 49 has an extending heel portion 54 adapted to enter one of a plurality of latching notches 55 formed in the retaining ring 25 when the latch element is in its lower position. Preferably at least four such notches 55 are provided although, as will become apparent hereinafter, it is only necessary that one opening be provided in the post.

The latch element 49 is urged into either of its two positions by a spring 56 anchored at its lower end by a stud 51 extending through the brackets 5| and secured therein a by split washers 58 pressed into annular grooves near each end of the stud 51. The sprin 56 is disposed substantially within the latch element 49 and the upper end is hooked through the top of the latch element 49. Thus, when the latch element is moved past dead center toward either its upper or lower position, it will be urged into such position by the spring 55 and held therein except when manually moved toward the opposite position. For convenience in manipulating the latch, the latch element 49 is provided with a handle 65 extending from the top thereof.

Normally, the latch element 49 is maintained in its upper position with the locking toes 52 entering the elongated opening 53 in the post-l l thereby locking the post H and spindle 2| positively together, thus permitting the chair post H and spindle to turn freely on the base It) without vertical displacement. When it i desired to change the adjustment of the height of the chair seat relative to the base 58, the latch element is withdrawn from the opening 53 and rocked downwardly toward its lower position. Owing to the toggle action provided b the spring 55, the latch element 49 is urged into its lower position, as soon as it has been moved past dead center, and in its lower position bears against the periphery of the retaining ring 25. The chair seat I2 is then rotated in the appropriate direction to rotate the chair post II and effect the desired height adjustment. Upon rotation of the chair seat through not more than one-quarter of a revolution, the latch element 49- is brought into position to enter one of the notches 55 and thus lock the spindle to the base l8. Further rotation of the chair seat effects rotation of the post relativeto the spindle and the adjustin nut carried by the post therefore is advanced along the stud, thereby elevating or depressing the post and the seat according to the direction of rotation of the latter.

If, when the latch element is moved from its upper to its lower position, it should happen to enter one of the notches 55, rotation of the chair seat would immediately initiate axial adjusting movement of the post H. When the desired height of the seat has been obtained the latch element 49 is raised to its upper position and the chair seat rotated to a suflicient angle (always less than one complete turn) to bring the toe 52 into position where it enters elongated opening 53. The spindle 2| is thereby locked to the post H and rotates therewith so that the adjusting nut and stud are rotated together and no vertical displacement of the post takes place;

the chair seat l2 thus is free to rotate in the base at the same elevation. Due to the pitch of the threads on the adjusting stud 34 and adjusting nut 35, the seat l2 will only be elevated or depresed a very slight distance during the partial rotation of the seat required to bring the latch element 89 into position to engage in the post opening 53 and there is no noticeable height adjustment during this partial rotation.

The seat 12 (Fig. 1) which may be of. anydesired contruction and preferably which takes the form of a cushion as is customary, is supported inent relative to the seat under the weight of the body of the user when the user leans back in the chair and is resiliently maintained in its more upright position.

The back rest support I3 is mounted for tilting movement by a tilting mechanism (Fig. 4) which includes a main yoke or frame 59 and an adjusting yoke or frame 10 mounted on a shaft H, pivotally supported in a tubular element 12. The tubular element l2 extends through and is supported in the chair post I I and is secured thereto by welding or other suitable means, the yoke 10 being mounted for rocking movement on the shaft and having its arms 18 disposed be tween the ends of the tube element 12 and the arms 15 of the main yoke 69. An abutment or shoulder 13 (Fig. 5) adjacent the outer ends of the shaft "H retains the side plates 15 in spaced relation on the shaft H and the yoke 69 is secured to the shaft as by nuts i l to maintain the said spaced relationship of the side plates. In this manner additional stability is provided for the main yoke 69 when the nuts 14 are tightened. The main or tilting yoke is formed by a pair of side plates connected at their front ends by a cross bar 76 preferably of square cross section and secured against turning as by engagement with short flanges Tl extending from the ends of the side plates 75. The adjusting yoke 78 includes a pair of side arms or plates 18 connected at their front ends by a cross bar 79 in a manner generally similar to the main yoke 89. The side arms [8 are bent in or offset at their ends to prevent rubbing against the side plates 75. A shaft 89 extends between and is secured to the rearward ends of the side plates l8 and serves as means for connecting a plurality of coil springs 8| to the adjusting yoke 70. The springs 8| are anchored at their upper ends to a shaft 82 (Fig. 5) secured in anchor brackets 83 depending from the seat mounting plate 54. By employing a plurality of springs 8| instead of a single spring, an improved spring action is obtaineol and the stresses on the associated members are more equally distributed.

The main yoke 59 (Fig. 2) and adjusting yoke 10 are connected at their front ends for simultaneously rocking movement about the pivot provided by the mounting shaft 1| and for mutual angular adjustment by a thread stud 85 extending through an enlarged opening 8'! in the cross bar 19 and threaded into the cross bar 16. The stud 86 has a knurled head 88 by which the stud can be turned and has an inwardly tapered portion which bears against a cupped washer 89 surrounding the stud intermediate the head 88 and the cross bar 79-. Thus it will be seen that the springs 3|, acting through the adjusting yoke l0 and the adjustable connection between the yokes 1i! and 69 provided by the stud 8t, tend to urge the yokes in a clockwise direction (as viewed in Fig. 2). The springs 8| are so dimensioned that the yoke 69 is maintained in position wherein upstanding limit lugs 84 bear against shock absorbent pad 85 secured to the under side of the seat support. The pads 85 preferably are made of non-metallic but relatively hard material, such as fiber, to provide a relatively noiseless stop for the yoke 69. The counterclockwise movement of the yokes against the urge of the springs 8! (as viewed in Fig. 4) is limited by the inturned lugs Tl striking against the under side of" the reinforcing plate 55, an opening 32 being provided in the plates 64 and 65 to receive the end of the stud 86 when the yoke 69 is rotated to its counterclockwise limit.

The tension on the springs 8| may be adjusted by turning the stud 86 to adjust the angular relation between the yokes 69 and I9. It will be seen that if the stud 86 is adjusted to bring the forward ends of the yokes closer together, a greater tension will be applied to the springs in their initial position and vice versa. Thus the yielding resistance to tilting of the back rest support can be adjusted to provide either a soft light resistance permitting relatively free tilting of the chair back, or a stiff heavy resistance preventing the chair back from being readily tilted, or any intermediate degree of yielding resistance.

The chair back rest support I3 is provided at its lower portion with a pair of spaced mounting arms 9| (Fig. 4) for mounting the back rest support on the side plates I5 of the yoke 69 and for securing the back rest support in adjusted angular position relative to the side plates 15 as hereinafter more fully described. For the purpose of mounting the back rest support I3 on the yoke 69, a mounting shaft 92 is provided which extends between and is secured in the rear ends of the side plates "I5 as by bolts 93, which latter carry bushings 94 (Fig. 5) extending through openings 95 in the mounting arms 9|. The two end bushings 94 extend freely through the openings 95 in the arms 9| and thus provide a self-aligning bearing for the back rest support I3. The shaft 92 and associated members not only serve as means for pivotally mounting the back rest support on the yoke 69, but also provides additional rigidity for the yoke 69.

Means are provided for securely locking the mounting arms 9| in angularly adjusted position with respect to the side plates I5 whereby, upon suitable simple manual manipulation, the back rest support may be adjusted on the side arms I5 to provide the desired angular position of the back rest support relative to the seat when the former is in its normally upright position and .the back rest sup-port may be then locked in adjusted position. A locking element which takes the form of a bolt 96 extends between and is carried fixedly in the forward ends of the adjusting arms 9|, openings 91 (Fig. 4), which may be of arcuate slot-like form, being provided in the side plates F5 to permit the bolt 96 to extend therethrough. It should be explained at this point that the width of each opening 91 is of such extent that the bolt 96 slides freely therein and does not bear against either side edge; the end portions, however, define the limits of adjustability or the relative extent of movement between the mounting arms 9| and the side plates I5. A locking lever 98 is pivotally carried on each side arm I5 and has an elongated slot 99 through which the bolt 96 extends. The locking levers 98 are mounted for free pivotal movement relative to the respective side plates 15 (except when restrained as hereinafter explained) and for this purpose a rod I99 is extended between and secured in the side plates I5 as by bolts |9|; the rod I99 also serves to impart added rigidity to the yoke 69.

For the purpose of restraining the locking levers 98 against angular movement about their respective pivots whereby they look the bolt 96 against movement about its pivot manually operable means are provided for frictionally retaining the locking levers in fixed positions of angular adjustment relative to the side plates. Such restraining means includes preferably a manually operable wing nut I93 threaded onto one end of the bolt 96 and adapted to be tightened on the bolt to clamp the locking levers 98 against the adjacent side plates 15, respectively. In order to provide a clamping abutment for the locking levers 98 a sleeve I91 and two washers I having a combined extent substantially equal to the spacing between the locking levers are interposed between the latter and are carried on the bolt 96. Three additional washers I96 are carried on the bolt 96, one being disposed between each of the side plates I5 and the adjacent mounting arm 9| and the third between the wing nut I93 and the adjacent arm. The bolt 96 is prevented from working out of position or turning, when the wing nut is tightened or loosened, by a keeper I94 secured on the mounting arm at the side of the chair away from the wing nut I93 and engaging a flat or a head I92 formed at the adjacent end of the bolt.

The locking levers 98 (Fig. 6) are so mounted and their slots 99 are so arranged that when the restraining means is released (by backing off the wing nut I93 from its clamping position) the locking levers are free to turn about their mutual pivot to permit the bolt 96 to slide along the slots 99 and move about its pivot 94. Thus, the back rest support I3 may be moved about its pivot 94, to, adjust its angular position on the side arms 15. To permit the locking levers 99 to move about their pivot, the latter is offset from a plane through the bolt 96 and the pivot about which it is movable. The several parts are shown in one extreme position of adjustment in Fig. 6, the back rest support I3 being in its most backwardly tilted position relatively to the chair seat. When the back rest support I3 is moved to its most upright position (indicated in broken lines) the bolt 96 slides to the opposite end of the slots 99, the locking levers 98 being moved in a clockwise direction (as viewed in Fig. 6) to a corresponding position (one of the locking levers being shown in this position in broken lines in Fig. 6).

The slots 99 in the locking levers 98 are arranged with their longitudinal side edges, extending at a wide acute angle to the direction of movement of the locking bolt 96. Hence, upon the application of a pivoting force on the side arms 9|, the locking bolt 96 exerts a force at a wide acute angle against a corresponding side edge of each slot. If the locking levers are not clamped against movement the locking bolt cams the locking levers about their pivot, the resistance to movement being relatively light. However, if the locking levers are clamped, the appropriate edge of each slot exerts a shear or binding action on the locking bolt which resists movement of the bolt along the slots and thus prevents movement of the bolt about its pivot. The angular posiion of the slot edge relative to the direction of movement of the bolt is such that a relatively light frictional clamping force on the locking levers is sufiicient to resist a relatively heavy force tending to move the locking bolt about its pivot.

The locking levers preferably are so arranged and their slots are so positioned that the angle between the longitudinal edges of the slots and the direction of movement of the locking bolt does not vary greatly throughout the entire range of angular adjustment between the side arms 9| and the side plates I5. Accordingly, a substantially uniform holding effect or shear action is obtained for any predetermined degree of tightening of the clamping means, regardless of the position of adjustment of the side arms and side plates. To provide this uniformity and the desired angular relationship between the slot edges and the direction of movement of the locking bolt, the pivot of the locking lever may be disposed so that a plane passing through this pivot and the locking bolt is approximately perpendicular to a plane through the locking bolt and its pivot; at the same time the slots in the locking levers are arranged with the plane of their longitudinal center lines making a wide acute angle with a plane through the pivots of the locking levers and the locking bolt. For example, the longitudinal center line of the slot may approximately bisect the angle between planes through the bolt and through the pivots of the bolt and the locking lever respectively. Preferably, the slot is arranged so that when the locking levers are in mid-position, the slot edges extend at an angle of slightly more than 45, for example, around 50, to the direction of movement of the bolt.

Thus, it will be seen that when it is desired to adjust the angle of the back rest support relatively to the seat, the wing nut M33 is loosened to release the clamping means. The back rest support then may be manually moved angularly about its pivot on the side arms it, the locking levers being free to move about their pivots to permit this angular movemen to take place without substantial resistance. When the desired angular adjustment is obtained, the back rest support may be secured in adjusted position by merely tightening the wing nut Hit. The wing nut IE3 is so located that it may be operated by the occupant of the chair from a sitting position in the chair.

The openings 9'! in the side plates are so shaped and are of sufficient width to permit free movement of the locking bolt therein when the back rest support is adjusted angularly on the side arms. These openings, however, serve to provide surfaces adjacent the locking bolt against which the clamping elements (i. e. the washers Hi6) may engage to permit the axial clamping force to be applied against the locking levers. These openings also may serve to limit the extent of angular movement of the locking bolt in the event there is a tendency to rock the backrest support beyond its normal adjusting movement and thus prevent damage to the locking levers.

The back rest support or back supporting member [3 (Fig. '7) preferably consisting of a light cast metal such as aluminum, supports two rods I08 disposed in parallel relationship and secured to bosses formed near the top and on the inside portion of the back rest support. The rods itii provide means for supporting a pair of clamp brackets its in slidable and adjustable relationship therewith and adapted to support the back rest cushion M. The brackets are secured to a cross connecting plate Ht such as by welding, which plate has end portions ii I extending outwardly from and located on the rear side of the rods E68. Arcuately shaped guiding elements i 92 are formed on the top and bottom of the brackets I09 to maintain a parallel sliding motion on the rods Hi8 when the back rest cushion is raised or lowered. ihe brackets I69 have outwardly directed ears H3, having openings to freely receive knurled-headed thumb screws Ht which also are threaded into the ends iii of the plate iii"; and When tightened secureiy clamp the plate and 10 brackets to the rods IE3. A forwardly directed lug I I5 is formed on each bracket and has an opening in the forward end thereof adapted to pivotally support a stud H6 secured in an ear formed on a pair of brackets Ill secured to the back of the cushion it.

Means are provided for adjusting the angular position of the back rest cushion relative to the back. supporting member which includes rubber headed thumb screws H8 carried in threaded collars 559 secured to the brackets Ill. The brackets ii? are mounted on the back of the cushion is in such position that the pivot studs I it are located above the horizontal center line of the cushion and the weight of the cushion below the said center line tends to maintain the cushion in a vertical position unless otherwise held out of this position by the rubber headed thumb screws contacting in the channel portions of the back supporting member 53. A rubber stop E26 secured to the back supporting member adjacent the top thereof is adapted to contact the back of the cushion if the said cushion is rotated counterclockwise (Fig. '7). The length of the lugs H5 and the height of the rubber stop 520 is such that both the height and tilting adjustments are accessible to the user of the chair without danger of pinching the fingers or hands while making said adjustments. 7

From the foregoing it will be seen that my invention provides a novel and improved chair which is of sturdy construction but which may be made light in Weight, and which may be manufactured and assembled readily and relatively inexpensively. The construction involves a minimum of machined parts or parts requiring close tolerances. Many of the parts may be made by casting or stamping, or from bar, rod or tube stock by simple operations. lhe parts may be assembled readily with a minimum of fitting or adjusting.

The seat height adjusting mechanism is simple but sturdy and may be operated conveniently. It is substantially housed and concealed and thus is well protected against dust and dirt; in addition the chair presents a neatand pleasing appearance. The swivel mounting requires no lubrication or other attention and is effective to maintain the chair post in stable upright position.

The mechanism for adjusting the angle of the back rest support is simple in construction and operation and is' effective to maintain the back rest support securely in adjusted position. The mechanism may be manipulated by the user from a sitting position in the chair and requires but little force to accomplish the desired adjustment and locking of the back rest support in adjusted position. The structure is such that stresses set up in the chair are equalized and bending and distortion are avoided.

The tilting mechanism which mounts the back support for tilting movement in its support is simple and rugged and may be adjusted from a sitting position in the chair to adjust the spring tension. The construction provides a balanced spring action and minimum distorting stresses in the chair members.

While I haveshown and described herein one form of structure embodying my invention, it will be understood that changes in details and arrangements of parts may be resorted to without departing from the spirit of the invention.

I claim:

1. A tilting back chair comprisin a seat support, a tilting frame and an adjusting frame,

means mounting said frames intermediate their ends for pivotal movement on said seat support independently about a common pivotal axis, means adjustably connecting said frames at the forward ends thereof for joint movement about said axis, spring means resiliently connecting said adjusting frame to said seat support at the opposite end of said adjusting frame from its connection to said tilting frame, and a back rest support carried by said tilting frame at the opposite end of said tilting frame from the ad justable connection between said frames.

2. A tilting back chair comprising a seat support, a tiltin yoke including spaced side arms and a cross-bar connected to said arms adjacent one end thereof, a back rest support carried by said arms adjacent the other ends thereof, an adjusting yoke including spaced side arms, and cross-bars connected to said adjusting yoke side arms adjacent the ends thereof, one of which is disposed adjacent the cross-bar of said tilting yoke, means pivotally mounting said yokes for independent pivotal movement on said seat support, means adjustably connecting the crossbar of said tilting yoke to said adjacent crossbar of said adjusting yoke for common pivotal movement on said seat support and for angular adjustment of said yokes relative to each other, and spring means connected between the other cross-bar of said adjusting yoke and said seat support for resiliently resisting pivotal movement in one direction of said yokes on said seat support.

3. An adjustable chair comprising seat supporting means, a positioning element mounted on said seat supporting means, a back rest support pivotally mounted on said positioning element for angular adjustment thereon, means for securing said positioning element and back rest support in relative angularly adjusted position, said securing means including a locking element carried by said back rest support, a locking lever pivotally mounted on said positioning element and having an elongated opening receiving said locking element for sliding movement therein permitting relative angular adjustment of said positioning element and said back rest support, and manually operable means for actuating said locking element to restrain said locking lever against movement about its pivot to hold said positioning element and said back rest support against angular movement relative to each other.

4. In an adjustable chair having a seat support member and a relatively adjustable back rest support member, a positioning element mounted on said seat support member, means pivotally mounting said back rest support on said positioning element, a locking element carried by said back rest support member for movement therewith, means including a locking lever pivotally carried by said positionin element and having an elongated opening slidably receiving said locking element, said last-named means being effective when said locking lever is restrained against movement about its pivot to hold said positioning element and said back rest support against angular movement relative to each other, and manually operable means for clamping said locking lever frictionally against said positioning element for restraining said lockin lever against movement about its pivot.

5. In an adjustable chair having a seat supporting member, a positioning element mounted on said seat supporting member, a back rest support pivotally carried by said positioning element, a locking element carried by said back rest support for movement therewith, a locking lever pivotally carried by said positioning element and having an elongated slot slidably receiving said locking element, and manually operable means for actuating said locking element to restrain said locking lever against movement about its pivot whereby upon the application of a pivoting force on said back rest support an edge of said slot exerts a shear action on said locking element to thereby hold said positioning element and back rest support against angular movement relative to each other.

6. In an adjustable chair having a seat sup:- porting member, a positioning element mounted on said member, a back rest support pivotally mounted on said positioning element, a locking element carried by said back rest support for pivotal movement therewith, a locking lever pivotally carried by said positioning element and having an elongated, linear opening receiving said locking element for sliding movement therein and formed with an edge shaped to exert a shear action on said locking element upon the application of a pivoting force on said back rest support when said locking lever is restrained against movement about its pivot, and manually operable means for restraining said locking lever against movement about its pivot to thereby cause said locking lever to hold said positioning element and back rest support against angular movement relative to each other.

7. In an adjustable chair having a seat supporting member, a positioning element mounted on said member, a back rest support, means pivotally mounting said back rest support on said positioning element, a locking element carried by said back rest support for pivotal movement therewith, a locking lever pivotally carried by said positioning element and having an elongated opening receiving said locking element for sliding movement therein and extending nonconcentrically to the pivotal axes of said locking lever and of said back rest support, and manually operable means for restraining said locking lever against movement about its pivot to cause the edge of said opening to exert a holding force against said locking element and thereby hold said positioning element and back rest support against angular movement relative to each other.

8. In an adjustable chair having a seat supporting member, a positioning element mounted on said member, a back rest support, means pivotally mounting said back rest support on said positioning element, a locking element carried by said back rest support for pivotal movement therewith, a locking lever pivotally carried by said positioning element and having an elongated opening receiving said locking element slidably therein and having edge portions extending at an acute angle to the direction of movement of said locking element about its pivotal axis to thereby exert a shear action on said locking element upon the application of a pivoting force on said back rest support when said locking lever is restrained against movement about its pivot, and manually operable means for restraining said locking lever against movement about its pivot to thereby hold said positioning element and back rest support against angular movement relative to each other.

9. In an adjustable chair having a seat supporting member, a positioning element mounted on said member, a back rest support pivotally mounted on said positioning element for angular adjustment thereon, a locking element carried by said back rest support for pivotal movement therewith, a locking lever mounted for pivotal movement on said positioning element about a pivot lying in a plane passing through said locking element and extending at an angle of approximately 90 to a plane passing through said locking element and its pivot, said locking lever having an elongated slot-like opening receiving said locking element for sliding, movement therein, said opening extending with its longitudinal center line lying in a plane approximately bisecting said angle, and manually adjustable means for restraining said locking lever against movement about its pivot whereby upon the application of a pivoting force on said back rest support, an edge of said opening exerts a shear action on said locking element and holds said positioning element and back rest support against angular movement relative to each other.

10. In an adjustable chair having seat supporting means, a positioning element mounted on said seat supporting means, a back rest support having a forwardly projecting element integral therewith, a locking element carried in the end of said projecting element, means supported on said projecting element intermediate said locking element and said back rest support for pivotally mounting said back rest support on said positioning element for relative angular movement therebetween, a locking lever pivotally mounted on said positioning element and having an elongated opening receiving said locking element for sliding movement therein to effect pivotal movement of said locking. lever when said back rest support is moved angularly relative to said positioning element, and manually operable means for clamping said locking lever frictionally against said positioning element to prevent pivotal movement of said locking lever to restrain said back rest support and positioning element against angular movement relative to each other.

11. An adjustable chair comprising seat supporting means, a positioning element mounted on said seat supporting means, a back rest support member, means pivotally mounting said back rest support member on said positioning element for relative angular movement therebetween, a looking element carried by said back rest support member for movement therewith, an arcuateshaped opening in said positioning element disposed concentric with said pivotal mounting means and freely receiving said locking element for concentric arcuate movement therein, the respective end portions of said arcuate-shaped opening defining the maximum extent of angular movement in each direction of said locking element and back rest support member relative to said positioning element, a locking lever pivotally carried by said positioning element and having a linear opening slidably receiving said locking element to effect pivotal movement of said locking lever on said positioning element during relative angular movement of said back rest support member and positioning element, and manually operable means for clamping said locking lever frictionally against said positioning element to restrain said locking lever against pivotal movement on said positioning element.

PETER MONDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,044,530 Hunn Nov. 19, 1912 2,054,557 Cramer Sept. 15, 1936 2,093,319 .l-Ierold Sept. 14, 1937 2,188,605 Herold Jan.'30, 1940 2,224,543 Harman Dec. 10, 1940 2,228,728 Paulson Jan. 14, 1941 2,281,037 Jones Apr. 28, 1942 2,359,918 Johnson Oct. 10, 1944 

